1. Field of the Invention
This invention relates to fuel injection valves and more particularly to an improved fuel system valve for use in an internal combustion engine.
2. Description of the Prior Art
A fuel injection valve of the type with which this invention is concerned is known from International Patent Disclosure PCT 96/02378. This known valve includes a central bore formed in a valve body, and a pistonlike, longitudinally displaceable valve member is disposed in this bore. A valve sealing face is formed on the end of the valve member toward the combustion chamber, and with this face the valve member cooperates with a valve seat, embodied on the end toward the combustion chamber of the central bore, to control at least one injection opening. The valve body is braced in the axial direction against a valve retaining body by a device in the form of a clamping nut.
By means of a taper of the valve member toward the combustion chamber, a pressure shoulder is formed on the valve member; this shoulder is disposed in a pressure chamber, embodied in the valve body, that can be filled with fuel via an inflow conduit extending in the valve body and in the valve retaining body. The inflow conduit passes through the contact face of the valve retaining body and valve body and is sealed off by the contact force of the clamping nut. To achieve an adequate contact pressure in the region of the passage of the inflow conduit and thus to assure secure sealing, the end faces must be ground flat with high precision, which is very complicated and thus expensive.
To increase the tightness, the contact pressure of the valve body at the valve retaining body must be increased. This is desired, however, only in the region of the transition point of the inflow conduit, since if an excessive force is exerted by the clamping nut on the valve body, the result can be deformation of the valve body, which has an unfavorable effect on the guidance of the valve member in the bore of the valve body. With the construction known thus far, it is not possible to increase the contact pressure locally in the region of the transition point of the inflow conduit.
The fuel injection valve according to the invention has the advantage over the prior art that the hydraulic pressure of the fuel in the inflow conduit is used to increase the contact force of the contact faces of two valve body parts in the region around the passage point of the inflow conduit. By means of a radial widening of the inflow conduit in the vicinity of the contact face of the valve body parts, and as the result of the hydraulic force of the fuel located in the inflow conduit, the radially widened portion is expanded in the axial direction of the inflow conduit. If the valve body parts are the valve body and the valve retaining body, for instance, then the face end, toward the valve body, of the radially widened portion embodied in the valve retaining body is pressed in the direction toward the valve body. This increases the contact pressure of the valve body and the valve retaining body at their contact face in the region of the passage of the inflow conduit and results in better sealing of the inflow conduit and a reduced demand in terms of the quality of the contact faces. It can be provided that a radially widened portion of this kind in the inflow conduit be embodied in both valve body parts contacting one another, or in only one of the two valve body parts.
In an advantageous embodiment of the subject of the invention, the radially widened portion is embodied as an annular groove extending all the way around on the inside wall surface of the inflow conduit. This makes simple, economical production possible and because of the rotationally symmetrical design of the radially widened portion, it assures a uniform contact pressure in the region of the passage of the inflow conduit through the contact face of the valve body parts. Advantageously, the transitional edges of the inflow conduit to the radially widened portion are rounded, so that at these points, no eddies can develop in the fuel flow through the inflow conduit.